There is a method in which an asphalt emulsion obtained by stirring asphalt and water in the presence of an emulsifier is used after it is mixed with an aggregate as one of road paving methods. In such a use, a cationic asphalt emulsion which is emulsified by a cationic surfactant is used because of good adhesion to an aggregate.
As a paving method using a cationic asphalt emulsion, a chip seal method is known in which the cationic asphalt emulsion is displayed on a road surface and then aggregates are scattered thereon. However, this method has the problems such as inferior durability of the paved body and therefore, paving methods called slurry seal or micro-surfacing have been proposed. This is a method in which an asphalt emulsion, an aggregate and water are separately mounted on a carrier car such that these materials are not in contact with each other and they are mixed using a mixer while the carrier car is running, to pave a road with the mixture.
However, the cationic asphalt emulsion largely varies in decomposition rate corresponding to the temperature of the aggregate and the characteristics (e.g., basic rock or acidic rock and water content) of the aggregate and the fluidity of the emulsion varies along with the change in decomposition rate. Therefore, in order to carry out proper paving, such works as to make pretests concerning the amount of a decomposition retardant to be added, the amount of water to be added and the like in advance are required. The slurry seal paving has various merits such as short paving time. However, since the cationic asphalt emulsion is used, the slurry seal paving has been insufficiently spread in such a situation as above mentioned. In actual, the slurry seal paving is practiced at present in a limited period of time which excludes high temperature and high moisture periods from the spring to the summer and during which the weather is relatively stable.
As examples of technologies used to solve these problems, U.S. Pat. Nos. 5328505, 5320671 and WO99/58491 are given. In U.S. Pat. Nos. 5328505 and 5320671, lignin is reacted with an polyamine to obtain an aminated lignin, which is used. Four or more hours are required to accomplish this reaction, giving rise to a problem concerning the productive efficiency of an emulsion. Also, in WO99/58491, a single branched polyamine is used for an asphalt emulsion. However, the time required for mixing aggregates may be secured insufficiently depending on the type of aggregate and it is desired to heighten commonness to aggregates, making it possible to secure the time required for mixing aggregates even if any type of aggregate is used.